GeO2 Content Research Articles

Structure and physical properties of sodium antimony germanate glasses

The structure and physical properties of sodium antimony germanate glasses with compositions 10Na2O − xSb2O3 − (90 − x)GeO2, x = 10−30 mol%, prepared by the melt-quenched route have been studied. It is observed from x-ray diffraction, SEM, density and oxygen molar volume, infrared (IR), differential thermal analysis (DTA), and optical absorption that single phase homogeneous glasses with a random network structure can be obtained in this system. The strength and connectivity of the glass network increase with GeO2 content. The main Ge−O stretching vibration also shifts to higher wavelength side. Two oxidation states of antimony, Sb3+ and Sb5+, are present, while the so-called “germanate anomaly” is absent in these glasses. This study discusses the probable structural reasons behind this type of behavior of these glasses.

Refractive Index Dispersion in Ternary Germanate Glasses

The refractive index dispersion in germanate oxyfluoride glasses of GeO2-P2O5-MF2 (M=Ca, Zn), which are developed for optical fiber application, is investigated in the 0.4-4 µ m wavelength range by the minimum deviation method. The prepared glasses have a GeO2 content varying from 80 to 30 mol%. The dispersion curves for these glasses tend to shift to shorter wavelengths as the GeO2 content is decreased. Material dispersions are also derived from the refractive index measurements and the zero-material dispersion wavelengths (λ0) are found in the vicinity of 1.5 µ m. On the basis of the empirical relationship between λ0 and the minimum loss wavelength (λ0), the λ min values are located at around 1.8 µ m. A minimum loss of as low as 0.08 dB/km is expected for the present germanate glasses.

D.c. and a.c. electrical properties of vacuum evaporated thin SiO/GeO2 films

The d.c. and a.c. electrical properties were studied for various compositions of SiO/GeO2 co-evaporated thin films carrying aluminium electrodes, in the temperature range 193–413 K. A.c. measurements were made over the frequency range 2x102–106Hz. The value of the d.c. activation energy was found to decrease with increasing GeO2 content in the SiO. In the region of high applied field (above 106 Vm−1, the conduction mechanism is governed by Schottky emission at the blocking contact. The a.c. electrical conductivity, σ(ω), varies with frequency according to the relation σ(ω) ∝ ωs, where the exponent s was found to be dependent on temperature and frequency. The a.c. conduction at low temperature was due to an electronic hopping process. The number of localized sites was estimated from the a.c. measurements for different compositions of SiO/GeO2 using the models proposed by Elliott and by Pollak, and the values are compared. The Elliott model satisfactorily accounts for the observed a.c. electrical results. A correlation was found between activation energy, optical band gap, conductivity and number of localized sites for the various compositions of SiO/GeO2 films. The relative dielectric constant, ɛr, and loss factor, tan δ, were found to increase with the increase of GeO2 content in the films.

X-Ray Absorption Analysis of Ge and Ga Environments in Ba-Gallogermante Glasses

ABSTRACTX-ray absorption spectroscopy has been used to characterize the local structure surrounding Ga and Ge in BaO-Ga2O3-GeO2 glasses. Based on comparisons with results for crystalline standards of known structure, Ge and Ga in all of the glasses are primarily in tetrahedral coordination; no evidence for octahedral coordination is observed. Bond length and coordination values derived from fitting calculations are fairly uniform for all glasses, however disorder increases with increase in BaO and decrease in GeO2 content, especially in the second shell surrounding Ge and Ga. Ge absorption edges for all glasses resemble smoothed BGG-An or GeO2 [quartz] edges. Ga absorption edges of the glasses also resemble the BGG-An edge which has two edge maxima, but in the glasses the relative intensities of the two maxima vary with composition.

Dielectric and pyroelectric properties of Pb5Ge3O11 ceramics

The pyroelectric coefficient of the (PbO)x(GeO2)(8−x) ceramics as a function of the PbO or GeO2 content close to x=5 was studied. The value of the pyroelectric coefficient increases with increasing content of the PbO up to x=5 and decreases above with an irregularity around x=5. From the frequency dependence of the complex dielectric constant the electric conductivity was determined. The temperature dependence of the electric conductivity is a function of poling. Unpoled ceramics have an activation energy of 0.70 eV. The observed dielectric relaxations in ceramics are equivalent to those in monocrystals.

A Raman study of the ring defects in GeO2-SiO2 glasses

The Raman spectra of GeO2-SiO2 glasses have been studied using samples of different GeO2 contents, which are found to have the general features of the spectrum of vitreous SiO2(v-SiO2). It is demonstrated that substitution of Ge for Si in the v-SiO2 network prevents the formation of ring structures. A new vibrational band located at 570-700 cm-1 was found in the spectra of high-GeO2-content samples (above 5.0 at.%GeO2). It is also shown that the W3 vibration of the v-SiO2 network is reduced in highly GeO2 doped GeO2-SiO2 glasses.

Formation mechanism of defect centers in GeO 2-doped silica glass

This paper describes the formation mechanism of defect centers in GeO2-doped silica glass. Both Si and Ge E′ centers are induced by fiber drawing in silica optical fibers with GeO2 contents below 0.4 mol%. However, Ge E′ centers alone are observed above the critical GeO2 content. On the other hand, in glass irradiated with γ-ray at room temperature, both Ge-associated centers (GACs) and Si E′ centers are observed in 0.4 mol% GeO2 content. However, GACs alone are observed in higher content. Furthermore, annealing causes not only a decrease in GACs but also an increase in Si E′ centers in irradiated silica glass with 0.4 mol% GeO2 content. The transformation from GACs to Si E′ centers is considered to result from the electron migration. The electron mean free path is estimated at about 1.4 ran from the nearest-neighbor interatomic distance between Ge atoms.

The Nature of the Reduced Defect and the Diffusion of GeO2 in Germaniadoped Vitreous Silica

AbstractDiffusion constants of GeO2 in vitreous silica and absorbances at 242 nm were determined as a function of temperature, time and oxygen content of the gas surrounding the samples during annealing. The samples were prepared by the PCVD method (Plasma‐activated Chemical Vapour Deposition). Computer modelling showed that the reduced germanium centre absorbing at 242 nm is an antistructure defect (germanium on an oxygen site) and not GeO, as suggested by other publications. The diffusion constant of O2 molecules, relevant in the computer model, is given by magnified image The GeO2 diffusion constant decreases at a given temperature with increasing oxygen content of the sample and increases with the GeO2 content. An average value is given by magnified image.

Glass Formation and Properties in the System Calcia‐Gallia‐Germania

The critical cooling rate for glass formation, Rc, was measured for four compositions in the system calcia‐gallia‐germania. The activation energy, E, and frequency factor, u, for the crystallization process were determined by reheating the glasses at varied constant heating rates and measuring the temperature of crystallization. Both E and v increased, with increasing germania content of the glass, whereas Rc decreased. The density, refractive index, and Abbe number were also measured; all decreased with increasing GeO2 content. These results are compared with those for calcia‐gallia‐silica glasses of comparable compositions.

Multicomponent Glasses of GeO2 and Sb2O3 with Bi2O3, T12O, andlor PbO

Previous studies on glass formation involving GeO2 with Bi2O3, TI2O, and PbO were extended by the use of Sb2O3. Wide areas of glass formation occur in the systems GeO2-PbO-Sb2O3 and GeO2-Bi2O3-Sb2O3 at all but the lowest GeO2 contents; the region of single-phase glasses in the system GeO2-Tl2O-Sb2O3 is severely restricted. Glasses were examined by powder X-ray diffraction, differential thermal analysis, thermomechanical analysis, and Archimedes’technique to obtain glass transition and crystallization exotherm temperatures, thermal expansion coefficients, and densities; these properties are presented in diagrams for the GeO2-Sb2O3 binary and for two ternary systems. Based on calculated values of Δo,the waveleneth for zero material dispersion. and dM/dΔ. the material disiersion slope at Δo, compositions in these systems may be useful for the construction of ultralow-loss optical waveguides in the 3 to 4 μm region.

Glass‐Forming Systems Involving GeO2 with Bi2O3, Ti2O, and PbO

The previously studied system GeO2‐Bi2O3‐TI2O was extended with the addition of PbO using air‐ and water‐quenched melted samples. Large areas of glass formation were found in the systems GeO2–Bi2O3–PbO and GeO2–PbO–Tl2O at all but the lowest GeO2 contents. Glasses were examined by powder X‐ray diffraction, differential thermal analysis, thermomechanical analysis, and Archimedes’technique to obtain glass transition and crystallization exotherm temperatures, thermal expansion coefficients, and densities, which are presented in diagrams for the GeO2‐PbO binary and for the two ternary systems. Based on calculated values of λ0, the wavelength for zero material dispersion, compositions in this system may be useful for construction of ultralow‐loss optical waveguides in the μm region.

On the physical properties of 20Fe2C380 [3B2O3 (1?x)PbO x GeO2] glasses

The results of X-ray, electron microscopy, magnetic measurements, Mossbauer effect, electron paramagnetic resonance and electrical resistivity studies on 20Fe2O380 [3B2O3 (1−x)PbOxGeO2] glasses are reported. Two sets of samples with 0⩽x⩽25 mol % GeO2 equilibrated at 1250° C and 1150° C, respectively, were investigated. All the samples were in the amorphous state. The number of ferrous ions in glasses equilibrated at 1250° C decreased by increasing the GeO2 content. In the case of the samples melted at 1150° C no evidence of Fe2+ ions was shown by magnetic and Mossbauer effect measurements. The magnetic susceptibility for T>80 K obeys a Curie-Weiss law and the effective moments of iron cations may be described by the free-ion values. The influence of the glass matrix composition and the equilibration temperatures on the intensities of g=2.00 and g=4.20 resonance lines is analysed. The EPR data suggest a clustering tendency of the iron ions in samples equilibrated at 1150° C. The resistivity measurements may be described by a mechanism involving electron hopping. The presence of two activation energies is shown. Finally, the experimental data are correlated in order to give a unitary description of the physical behaviour of the analysed glass system.

The Effect of Temperature on the Response of Glass-Clad Optical Waveguides to Ionizing Radiation

An investigation was made on the effects of pulsed ionizing radiation on the attenuation of SiO2 fiberoptic waveguides doped with GeO2, B2O3 and P2O5. Data were taken over time, temperature, and wavelength ranges of interest for long-length fiber-optic communication applications. For fibers containing only GeO2 and B2O3, operation at 1.06 #x003BC;m reduced by a factor of approximately 10 the radiation sensitivity among the fibers examined when compared with 0.8-#x003BC;m operation. The fiber with the lowest GeO2 content (before deposition) showed the lowest radiation sensitivity of the fibers investigated. For systems applications, attention should be paid to operation at low temperature where large radiation-induced losses could persist at both wavelengths for long times following the irradiation pulse. The addition of small amounts of phosphorus reduced the low-temperature response, but also increases the radiation sensitivity at high temperatures.